Completely dead.

[hoover]

I’ve got a weird intermittent issue, it’s happened twice, and is unpredictable.
Everything is normal to start with, however on these two occasions when I have parked the car and switched off, I noticed that I couldn’t open the rear hatch with the key. On checking other stuff, found the whole system dead. Now the strange thing. Wait 15 minutes or so, and the car is back to normal and will start up. Most disconcerting !
If there are any ideas out there, I’d be pleased to hear from you, thanks.

[Jfrahm]

What system is dead?

If the whole electrical system goes dead it's usually a loose battery cable or bad battery cable end.

[hoover]

Thanks for reply. The whole electrical system dies, it’s not until I hear the radio start to play, that I know the system is back to normal. I will certainly check the battery connections. If it’s to do with a bad battery connection etc, I can’t understand why, in time, the fault goes away.

[944 Ecology]

Originally Posted by hoover

If it’s to do with a bad battery connection etc, I can’t understand why, in time, the fault goes away.

That's because it's an intermittent problem getting ready to fail permanently (on a dark night, unlit road, during a rain storm, no cell phone coverage, etc.)

But seriously, the best time to diagnose an intermittent problem is when the problem is happening. Carry a voltmeter, a test light, etc. and be prepared to spend a few minutes checking the voltage at various places (e.g. the fuse box) and checking the grounds for voltage drop when you are having a problem.

[originalowner]

Originally Posted by hoover

I can’t understand why, in time, the fault goes away.

Connection heats up while driving, disconnects. Connection cools down when stopped, reconnects.

While driving, power is supplied by the generator. Battery positive and ground are suspect.

[hoover]

Thanks for your replies I have cleaned the battery connections and noticed that a wire from what I believe is the immobiliser unit, was trapped between the bottom of the battery and the metal shelf on which it sits. On inspection this insulation of this wire was slightly damaged. I’m now thinking this could be a possible cause of the issue, maybe expanding and contracting depending on temperature. The wire concerned is shown in the picture.